Refactoring on the operators: negation is now being handled globally

Other minors changes were also made, including adding the prefix `m_'
to all the members of the class.

src/operators/detect_xss.cc

@@ -41,10 +41,6 @@ bool DetectXSS::evaluate(Transaction *transaction, const std::string &input) {
 #endif
     }
 
-    if (negation) {
-        return is_xss == 0;
-    }
-
     return is_xss != 0;
 }